With the continuous progress of science and technologies, the fingerprint recognition technology is becoming increasingly mature, and the applicable field thereof becoming increasingly extensive. For example, the fingerprint recognition technology may be applied to the access control system (such as punching in and out for work, or home security system), electronic terminal unlocking and the medical field, etc. In the medical field, the finger moisture can be used for representing the human health information. Therefore, measurement of the finger moisture can provide reference data for medical diagnosis.
In general, all of the conventional fingerprint collection technologies would just directly collect a user's fingerprint without taking into consideration the finger moisture, in which case the collected fingerprint image is prone to be unclear when the finger is too dry or too wet, thus the quality of the collected fingerprint image is affected. On the other hand, some of the fingerprint collection technologies would first measure the finger moisture by comparing the collected image with the predefined standard image when collecting the fingerprint, to determine whether the finger is too wet or too dry.
However, the above manner for determining whether the finger is too wet or too dry has the following disadvantages: the contrast of the collected image is prone to be disturbed by the undulation of the image background, noise, etc., resulting in that the contrast of the collected image has low accuracy and is then difficult to be used accurately in quantitative measurement of finger moisture.